Reinforced air cargo pallet

ABSTRACT

An air cargo pallet includes a base metal sheet and extruded edge rails. A metal reinforcing strip is attached to a top surface of the metal base sheet and can run substantially across the entire width of the base sheet. The reinforcing strip divides the unsupported area of the base sheet, thereby reducing the effects of “oil canning” on the base sheet. Lower cost metals may be used for forming the base sheet.

BACKGROUND

Air cargo pallets are commonly used to support and secure cargo duringtransportation via aircraft, ground vehicles, and ships. A widely usedair cargo pallet is made of a base sheet of aluminum with edge railextrusions at each side or edge.

The base sheet of a typical air cargo pallet is often subjected toservice-induced “oil canning.” Oil canning is a condition where anotherwise substantially flat metal sheet becomes slightly deformed. Oilcanning can result from residual stresses induced or redistributedduring production, slitting, perforating, forming, or fabrication of themetal sheets. Improper handling, as well as routine service, can alsocause oil canning. Oil canning of the base sheet of an air cargo palletcan be detrimental to the pallet's operation. After a certain degree ofdeformation occurs, the pallet becomes unusable.

Oil canning of the base sheet of an air cargo pallet often results fromstresses induced on the bottom surface of the base sheet that occurduring repetitive service cycles. Air cargo pallets, and the containersthat they support, are typically used to transport up to 15,000 pounds(or more) of cargo, and are generally conveyed over a variety ofconveying surfaces and devices. For example, air cargo pallets may beconveyed on roller ball conveyors. These conveyors make rolling pointcontact with the bottom surface of the base sheet. This rolling pointcontact induces bending stresses in the bottom surface of the basesheet, which may eventually lead to permanent deformation of the basesheet as the yield strength of the base sheet is exceeded by thecompressive forces applied by the roller balls.

To reduce the effects of oil canning, the bottom sheets of air cargopallets are often made from a high strength aluminum alloy, such asaluminum alloy 7075T6. While this high strength aluminum alloy has beenrelatively effective at preventing substantial oil canning in a pallet'sbase sheet, it is typically expensive and/or in short supply. Thus,durable air cargo pallets may be relatively expensive to manufacture. Aneed exists for a more cost-effective, durable air cargo pallet.

SUMMARY OF THE INVENTION

An air cargo pallet includes one or more reinforcing strips attached toa top surface of the base sheet of the pallet. The reinforcing stripdivides the unsupported area of the base sheet into two substantiallyequal sections. This reduces the effects of “oil canning” on the basesheet, and allows the use of lower-cost metals for forming the basesheet. The reinforcing strip may run substantially across the widthand/or the length of the base sheet.

Other features and advantages of the invention will appear hereinafter.The features of the invention described above can be used separately ortogether, or in various combinations of one or more of them. Theinvention resides as well in sub-combinations of the features described.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein the same reference number indicates the sameelement throughout the several views:

FIG. 1 is a plan view of an air improved cargo pallet.

FIG. 2 is an enlarged view of one corner of the air cargo pallet shownin FIG. 1.

FIG. 3 is a section view taken along line 3-3 of FIG. 2.

FIG. 4 is a top plan view of a base sheet of an air cargo palletincluding a reinforcing strip, according to one embodiment.

FIG. 5 is a section view, taken along section A-A, of the reinforcingstrip shown in FIG. 4.

FIG. 6 is a partial plan view of a reinforcing strip used to reinforceone or more base sheets of an air cargo pallet.

FIG. 7 is a top plan view of one of two base sheets of an alternativeair cargo pallet.

DETAILED DESCRIPTION OF THE DRAWINGS

As shown in FIGS. 1-3, an air cargo pallet 10, according to oneembodiment, includes a base sheet 14, with an edge rail extrusion 12riveted onto each of the four edges of the base sheet 14.

The air cargo pallet 10 typically has a length L of approximately 100 to150 inches, and a width W of approximately 80 to 100 inches. The palletmay also be made to a standard size with a length of approximately 108inches or 125 inches, and a width of approximately 88 or 96 inches.

Referring to FIG. 4, the base sheet 14 generally has a width X that isabout 7 inches less than the entire width of the pallet (including theedge rails). The width X is accordingly generally about 81 or 89 inches.The base sheet 14 similarly has a length Y that is about 7 inches lessthan entire length of the pallet (including the edge rails). The lengthY is accordingly generally about 101 to 118 inches.

A reinforcing strip 30 is attached to the upward-facing, or top, surfaceof the base sheet 14 via screws 32, rivets, or other suitable fasteningmeans. The reinforcing strip 30 in the design shown is locatedsubstantially at or near the longitudinal centerline L of the base sheet14 (or pallet 10), and runs substantially across the entire width X ofthe base sheet 14. The reinforcing strip is preferably made of metal,such as aluminum or steel, but may also be made from another material.The reinforcing strip 30 may be a tie bar, or any other suitablereinforcing device or structure. The reinforcing strip or stripsgenerally are parallel to the shorter sides of the pallet.

Oil canning of a metal sheet, in general, is inversely proportional tothe yield strength of the metal sheet, and is directly proportional tothe sheet's unsupported surface area, its moment of inertia (i.e., thecube of its thickness), and the loads applied. The reinforcing strip 30divides the unsupported surface area of the base sheet 14 into twosections. As a result, oil canning of the base sheet 14 is reduced byapproximately one half (assuming that all other factors are equal). Thiscan in principle effectively double the service life of the base sheet14.

Oil canning also tends to deform the base sheet. This can cause the edgerails to lift up, making the pallet unusable. With the base sheet 14divided into two pieces, the tendency for the edge rails to lift up isreduced. This prolongs the service of the pallet.

In addition, pallet designs including a reinforcing strip allow for theuse of lower strength, lower cost, and more readily available aluminumalloys as the base sheet material. For example, the base sheets of manyconventional air cargo pallets are made from heat-treated aluminum alloy7075T6, with a thickness of approximately 0.160 inches. By including areinforcing strip 30 on the base sheet 14, similar resistance to oilcanning can be achieved using other aluminum alloys having lower yieldstrength, with only a slightly greater base sheet thickness.

Other aluminum alloys are typically significantly less costly thanaluminum alloy 7075T6 and is also more easily obtained (regardless ofcost). Thus, the use of other aluminum alloys provides substantial costsavings, particularly when several air cargo pallets are being produced.Since other aluminum alloys have lower strength in comparison toaluminum alloy 7075T6, base sheets made of other aluminum alloys can bemade slightly thicker, to achieve equivalent strength. This increase inthickness, however, does not also result in a proportional increase inweight, because other aluminum alloys typically weigh less than aluminumalloy 7075T6. As one example, a base sheet of aluminum alloy 5083H24P isused instead of aluminum alloy 7075T6. The 5083H24P base sheet is 8%thicker than the 7075T6 base sheet. The aluminum alloy 5083H24P,however, is approximately 4.5% lighter than aluminum alloy 7075T6.Accordingly, using the lower cost and more abundant aluminum alloy5083H24P as the base sheet increases the overall weight by onlyapproximately 3.5%. This is relatively insignificant compared to theconsiderable cost savings that are realized by using the lower costalloy. Various other examples using other lower cost aluminum alloys canalso be made. The term other aluminum alloys as used here means aluminumalloys having a yield strength less than the yield strength of 7076T6aluminum alloy.

In an alternative embodiment, the overall base sheet structure of theair cargo pallet 10 includes two coplanar smaller base sheets 14′, asillustrated in FIG. 5. This design may be advantageous in somecircumstances, since two smaller sheets of aluminum, or of another metalmaterial, are often less costly than one large sheet having the samesurface area as the two smaller sheets combined. Moreover, the smallersheets may be more readily available than the larger sheets. Forexample, two sheets of 60×81 inch aluminum alloy 7075T6 cost less(typically about 25% less) than a single sheet of 81×120 inch aluminumalloy 7075T6. Thus, cost savings can often be realized by using twosmaller base sheets, as opposed to using a single larger base sheet.

FIG. 7 illustrates a first smaller base sheet 14′, which may have awidth Y′ that is substantially equal to one half the length Y of thebase sheet 14 described above (e.g., approximately 60 inches versusapproximately 120 inches). A second smaller base sheet 14′ (not shown)can have the same dimensions as the first smaller base sheet 14′.Accordingly, when the two smaller base sheets 14′ are joined together,their combined width (i.e., the overall base sheet length) willgenerally equal the length Y (e.g., approximately 120 inches) of thebase sheet 14. The length X′ (i.e., the overall base sheet's width) ofeach base sheet is typically equal to the width X of the base sheet 14described above (e.g., approximately 81 inches). Thus, when the twosmaller base sheets 14′ are joined, the overall area of the two smallerbase sheets 14′ is about the same as the area of the base sheet 14described above.

The interior adjoining sides 34 of the two smaller base sheets 14′ mayabut or contact each other, and are joined together via the reinforcingstrip 30. As shown in FIGS. 5 and 6, the reinforcing strip 30 mayinclude two rows of screws, rivets, or other fasteners 32, runninglengthwise along the reinforcing strip 30. One of the rows of fasteners32 can attach the reinforcing strip 30 to the top surface of one of thesmaller base sheets 14′, and the other row of fasteners 32 can attachthe reinforcing strip 30 to the top surface of the other smaller basesheet 14′, as is best shown in FIG. 5. Thus, the two smaller base sheets14′ may be joined to each otherr by the reinforcing strip 30.

Any suitable number of base sheets and/or reinforcing strips may beincluded in the air cargo pallet 10. For example, a single base sheet 14may include a single reinforcing strip 30, or may include two or morereinforcing strips 30. If two or more reinforcing strips 30 are used,the reinforcing strips 30 can be spaced approximately equidistantly fromone another, and from the outer edges of the pallet 10. However, thereinforcing strips 30 may be arranged in other ways as well, to bettermeet the design requirements of any specific pallet.

The pallet's overall base sheet structure may include one base sheet 14,two base sheets 14′, or three or more base sheets. Each pair of adjacentbase sheets is preferably, but not necessarily, joined by a reinforcingstrip 30. Alternatively, only a single reinforcing strip 30 may beincluded on the overall base sheet structure of the air cargo pallet 10,regardless of the number of base sheets used. Thus, various combinationsand numbers of base sheets and reinforcing strips 30 may be used. Thebase sheet thickness when using other aluminum alloys will generally beabout 0.16 or 0.17 to about 0.25 inches. As shown in FIG. 5, thereinforcing strip will generally have a thickness greater than the basesheet, for example, 0.18 or 0.19 to about 0.38 inches. The shoulders orupper edges of the reinforcing strip 30 may optionally be chamfered, asshown in FIG. 5, or they may be radiused. Alternatively, they may befully angled to provide a ramp surface from the top surface of the basesheet running up to the top surface of the reinforcing strip. Thereinforcing strip may also be segmented or intermittent, i.e., withspaced apart strip segments, in certain applications.

In another alternative embodiment, one or more reinforcing strips mayrun lengthwise across the one or more base sheets of the air cargopallet 10, as opposed to, or in addition to, running widthwise acrossthe one or more base sheets. The lengthwise reinforcing strip(s) may runsubstantially across the entire length of the base sheet (or of thecombined base sheets), or may run a shorter distance.

The inclusion of one or more reinforcing strips substantially reducesthe unsupported area of the one or more base sheets of an air cargopallet, and therefore significantly reduces oil canning in the basesheet(s). As a result, the service life of the base sheet, and thepallet itself, may be dramatically increased. Furthermore, lower costmaterials, having a lower yield strength than conventional base sheetmaterials, may be used to form the base sheet(s), thus significantlyreducing the total cost of the air cargo pallet.

The preferred dimensions and materials of the various components of theair cargo pallet 10 may vary depending on specific design requirements.Accordingly, any pallet having one or more base sheets having areinforcing strip or element is within the scope of the invention.

While embodiments and applications of the invention have been shown anddescribed, it will be apparent to one skilled in the art that othermodifications are possible without departing from the inventive conceptsherein. The invention, therefore, is not to be restricted except to thefollowing claims and their equivalents.

1. In a cargo pallet of the type having a base sheet and edge railsattached at edges of the base sheet, the improvement comprising: atleast one reinforcing strip attached to a top surface of the base sheetand extending substantially across the width of the base sheet, and withthe base sheet having a yield strength less than aluminum alloy 7076T6.2. The cargo pallet of claim 1 with the base sheet having a thickness ofabout 0.16 to about 0.25 and with the reinforcing strip having athickness greater than the thickness of the base sheet.
 3. The cargopallet of claim 1 with the base sheet divided into two separatesections, and with the separate sections attached together via thereinforcing strip.
 4. The cargo pallet of claim 3 wherein the separatesections have equivalent dimensions.
 5. The cargo pallet of claim 4wherein the reinforcing strip runs substantially across the length ofeach of the base sheet sections and with the sections abutting eachother.
 6. The cargo pallet of claim 3 wherein reinforcing strip hasangled or radiused sides.
 7. The cargo pallet of claim 1 with thereinforcing strip extending parallel to the shorter edges of the pallet.8. The cargo pallet of claim 1 wherein the reinforcing strip is locatedsubstantially at the lengthwise midpoint of the first base sheet.
 9. Thecargo pallet of claim 1 wherein a plurality of reinforcing strips areattached to a top surface of the base sheet.
 10. The cargo pallet ofclaim 9 wherein the plurality of reinforcing strips are substantiallyequidistantly spaced from one another.
 11. The cargo pallet of claim 1wherein the reinforcing strip runs substantially across the length ofthe base sheet.
 12. A cargo pallet, comprising: a first metal basesheet; a second metal base sheet abutting to the first base sheet; and areinforcing strip attached to a top surface of the first base sheet andto a top surface of the second base sheet; and first and second edgerail extrusions attached to outer edges of the first base sheet, andthird and fourth edge rail extrusions attached to outer edges of thesecond base sheet.
 13. The cargo pallet of claim 12 wherein thereinforcing strip runs substantially across the length of each of thefirst and second base sheets where the first base sheet abuts the secondbase sheet.
 14. The cargo pallet of claim 12 with the first and secondmetal base sheets comprising an aluminum alloy having a yield strengthless than alloy 7076T6 and having a thickness greater than about 0.16inches.
 15. The cargo pallet of claim 12 wherein the first and secondbase sheets are riveted to the edge rails and to the reinforcing strip.16. The cargo pallet of claim 12 wherein the first and second basesheets each have approximately the same length and width.
 17. In a cargopallet of the type having a base sheet and edge rails attached to theedges of the base sheet, the improvement comprising: the base sheetcomprising an aluminum alloy having a yield strength less than aluminumalloy 7076T6; and reinforcement means for reinforcing the base sheet,with the reinforcement means attached to a top surface of the basesheet.
 18. The cargo pallet of claim 17 with the reinforcement meansdividing the base sheet into two or more substantially equal areas.